Powdered metal bearings



Jan. 21, 1964 CLAPP 3,118,272

POWDERED METAL BEARINGS Filed June 8, 1962 I NVE NTOR United States Patent 3,118,272 POWDERED METAL BEARINGS Nathaniel D. Clapp, Prides Crossing, Mass., assignor to Wakefield Bearing Corporation, Wakefield, Mass, a corporation of Massachusetts Filed June 8, 1962, Ser. No. 201,061 7 Claims. (Cl. 57-120) This invention relates to porous metal bearings of the type which are designed to engage high speed travelers, for example textile spinning and twisting rings and actuating cams in knitting machinery.

Bearings of the above type bear against travelers moving at relatively high speeds and have relatively small areas in contact therewith at any instant. Such bearing contact results in a type of wear sometimes referred to as chattering or fretting wherein the bearing assumes a Wavy or undulating contact surface which interferes with operation and necessitates replacement of the bearing. In the case of knitting machine cams, sometimes referred to as sinker cams, this undulating or chattering wear has resulted in an unduly short life of the cams and occasionally interferes with the operation of the knitting needles. Attempts to use various steel and other alloys substantially to extend the wear life of such cams have not been successful.

Spinning or twisting rings heretofore in use have further limitations in that heat and wear have limited the rate of traveler movement to a maximum of approximately 5,000 to 6,000 feet per minute, whereas higher speeds are desirable.

The present invention has for its principal object the provision of improved bearings of the above type which are subject to limited area contact at high speed, which are subject to chattering wear and which provide substantially improved results, especially in increased Wear life and in permiting higher linear speeds for a traveler.

In accordance with the present invention these and other objects are obtained by a bearing of powdered, compressed, and sintered material containing powdered crystalline aluminum oxide (A1 0 The bearing consists essentially of a compressed and sintered mixture comprising by weight aluminum oxide 1.5 to 4.0%, car bon O to 1.0%, nickel O to 7%, copper 0 to with the balance substantially all iron. The preferred composition according to this invention comprises a pressed and sintered mixture as follows:

Compositions containing nickel, preferably about /2 to 5% by weight, are much preferred and give substantially superior results. The inclusion of nickel improves the hardening and wearabil-ity of the bearing, provides a better crystalline structure and greater hardness, and is believed to hold the abrasive particles more firmly in the matrix. While copper may be included, if desired, compositions in which this element is omitted are preferred. For some purposes hard particles such as the carbides of vanadium, tungsten, chromium, molybdenum or silicon may be substituted for the preferred A1 0 In the drawing,

FIG. 1 is a microphotograph of a nital etched, porous bearing structure in accordance With this invention and after quenching, the magnification being 220x;

FIG. 2 is a radial section of a spinning ring and associated traveler T;

FIG. 3 is a radial section of a twisting ring and traveler T;

FIG. 4 is a plan view of a portion of a textile sinker cam assembly; and

FIG. 5 is a section on the line 55 of FIG. 4.

The conventional sinker cam assembly shown in FIGS. 4 and 5 comprises a circular channel guide 10 with upstanding concentric flanges 11 and 12-, a sinker or traveler 13 reciprocating in slot 14 in guide 10, and an actuating or sinker cam 15 having opposed cam surfaces 16 and 17 which engage shoulders 18 and 19 of sinker 13 to reciprocate the same. Cam 15 may be oscillated within channel 10 to impart a reciprocating motion to the sinker 13 or, more conventionally, a plurality of cams 15 may be circumferentially moved to engage in succession a plurality of sinkers 13.

The spinning ring 20 (FIG. 2), the twisting ring 21 (FIG. 3), and cam 15 are all made from the preferred powdered mixture previously stated. The nickel was carbonyl nickel, grade B, of the International Nickel Co. having particle sizes from 2.9 to 3.6 microns; the carbon was graphite, grade FG of Asbury Graphite Mills of particle size 15 to 44 microns; the aluminum oxide Was crystalline Levigated Alumina of the Norton Company having a particle size of 3 to 6 microns and sold as a lapping compound; and the iron powder was grade 365 of the Easton Metal Powder Co. having particle sizes distributed as follows, percentages being by Weight:

Mesh: Percent .35 2.15 17.43 +200 32.71 +325 24.95 325 22.41

Percent CO 20.7 H 38.8 CH, 0.4 N 4. 40.1

After sintering, the parts were allowed to cool in the protective atmosphere to room temperature. They were thereafter coined in dies to the desired dimensions under pressure, for example from 30 to 50 tons per square inch. The coining pressure can be varied somewhat in order to obtain the desired final dimensions. It is preferred that the novel bearings of this invention be coined directly to final size and rfinish since the machining and lapping decrease the effectiveness of the bearing surface. It is believed that the coining pressure thoroughly embeds the abrasive aluminum oxide particles in the iron matrix so as to substantially limit their cutting ability. Careful grinding is less detrimental than machining or lapping.

While spinning or twisting rings may be gas carburized if desired by the procedure described below, such carburization is usually not necessary. However, it is preferred to gas carburize the knitting cams as follows: The coined cams are loaded into a pit type furnace, brought to 1520" F. in a carburizing atmosphere comprising the above protective atmosphere enriched with 1 part by volume natural gas for each 10 parts protective atmosphere, held at this temperature until the dew point of outcoming atmosphere drops and becomes steady at 40 F.

or below, and then quenched in water at room temperature.

Bearings in accordance with this invention have a desirable combination of properties, including highstrength, high load carrying capacity, good hardness (e.g. Rockswell C60), low eoeflicient of friction, and ,good Wear and heat resistance at modest cost. They are also noncatalytic when used with impregnating oils. Bearings in accordance with this invention preferably have from 10 to 25%, and preferably about '18 to 25%, porosity and are vacuum impregnated with oil prior to use.

As pointed out above, spinning and twisting rings heretofore employed have been limited to linear traveler speeds of about 5 to 6 thousand 'feet per minute. However, with rings made in accordance with this invention, speeds as high as 10,000 ft. per minute or more have been obtained. Moreover, rings of small diameter are now feasible. Knitting cams of the instant invention have replaced 52100 tool steel cams with substantially superior results.

it is to be understood that the foregoing description is intended for illustration only and that the invention includes all modification falling Within the scope of the appended claims.

I claim:

I. A porous bearing having a surface adapted for engagement with a high speed traveler which has a small area in contact therewith, said bearing consisting essentially of a pressed and sintered powdered mixture comprising by Weight approximately 0 to 1.0% carbon, /2 to 5% nickel, 0 to 5% copper, -1.5 to 4.0% A1 0 and the balance substantially all iron.

2. A porous bearing in accordance with claim 1 wherein said mixture comprises-about 2% A1 0 0.75% carbon, 3.5% nickel, and .the balance substantially all iron.

3. A porous textile spinning or twisting ring consisting essentially of .a pressed and sintered powdered mixture comprising by weight approximately 0 to 1.0% carbon, /2 to 5% nickel, 1.5 to 4% A1 0 and the balance substantial-ly all iron, said ring being characterized by high wear resistance, low coefficient of friction, and permitting high traveler speeds.

4. A textile ring in accordance with claim 3 wherein said mixture is approximately:

Percent A1 0 2 Carbon 0.75 Nickel 3 .5 Iron 93 .75

5. A knitting needle actuating cam consisting essentially of a pressed and sintered powdered mixture comprising by weight approximately 0 to 1.0% carbon, /2 to 5% nickel, 1.5 to 4% A1 0 and the balance substantially all non.

6. A knitting cam in accordance with claim 5 having a gas carburized surface.

7. A knitting cam in accordance with claim 6 wherein said mixture is approximately: 

1. A POROUS BEARING HAVING A SURFACE ADAPTED FOR ENGAGEMENT WITH A HIGH SPEED TRAVELER WHICH HAS A SMALL AREA IN CONTACT THEREWITH, SAID BEARING CONSISTING ESSENTIALLY OF A PRESSED AND SINTERED POWDERED MIXTURE COMPRISING BY WEIGHT APPROXIMATELY 0 TO 1.0% CARBON, 1/2 TO 5% NICKEL, 0 TO 5% COPPER, 1.5 TO 4.0% AL2O3 AND THE BALANCE SUBSTANTIALLY ALL IRON. 